Operation method of electric power source device, electric power source device, and high-frequency treatment system

ABSTRACT

An operation method of an electric power source device for operating a high-frequency treatment instrument configured to perform a high-frequency treatment on a biological tissue includes causing a high-frequency electric power source circuit to output electric power; acquiring an initial impedance value in a first period from a start of the output; determining an increase rate of an output voltage relative to time; increasing the output voltage of the high-frequency electric power source circuit in accordance with the increase rate in a second period; acquiring the value relating to impedance of the biological tissue in the second period; and terminating the second period after the value relating to the impedance reaches a minimum value.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation. Application of PCT Application No.PCT/JP2016/064615, filed May 17, 2016 and based upon and claiming thebenefit of priority from prior Japanese Patent Application No.2015-150476, filed Jul. 30, 2015, the entire contents of all of whichare incorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to an operation method of an electricpower source device for operating a high-frequency treatment instrument,an electric power source device, and a high-frequency treatment system.

2. Description of the Related Art

In general, there is known a high-frequency treatment system whichperforms a treatment by grasping a biological tissue, which is atreatment target, by a pair of grasping members, and by supplyinghigh-frequency electric power to the biological tissue. In this system,the biological-tissue grasped by the grasping members is heated by ahigh-frequency current flowing through the biological tissue. Thishigh-frequency treatment system is used for, for example, sealing ablood vessel. In the high-frequency treatment system, in order toimprove the precision and efficiency of the treatment, it is required toappropriately adjust an output voltage and an output current.

For example, Jpn. Pat. Appln. KOKAI Publication No. H8-98845 discloses atechnique relating to controlling an output by paying attention to animpedance value of a biological tissue. Specifically, in this technique,a maximum value and a minimum value of the impedance value measured atan initial stage of a treatment are specified. The impedance value,which is measured during the treatment, rises after taking a minimumvalue. In the process of rising, the output is stopped when theimpedance value reaches a predetermined value between the specifiedmaximum value and minimum value. It is considered preferable that thisvalue between the maximum value and minimum value is, for example, amean value between the maximum value and minimum value.

In addition, for example, Jpn. Pat. Appln. KOKAI Publication No.2012-196458 discloses a technique relating to setting a target valuewith respect to the transition of the impedance value during thetreatment, and controlling the output such that this target value andthe measured actual impedance value become equal.

In the high-frequency treatment system, since the adjustment of theoutput voltage and output current affects the precision and efficiencyof the treatment, it is required that the output voltage and outputcurrent be adjusted more appropriately. In addition, it is known thatthe optimal output voltage and output current vary in accordance with atreatment target. Accordingly, it is required that the output voltageand output current be adjusted in accordance with a treatment target.

BRIEF SUMMARY OF THE INVENTION

According to an aspect of the invention, an operation method of anelectric power source device for operating a high-frequency treatmentinstrument configured to perform a high-frequency treatment on abiological tissue includes causing, by a control circuit, ahigh-frequency electric power source circuit to output electric power;acquiring, by the control circuit, an initial impedance value, which isa value relating to an impedance of the biological tissue, in a firstperiod from a start of the output; determining, by the control circuit,an increase rate of an output voltage relative to time, based on theinitial impedance value; increasing, by the control circuit, the outputvoltage of the high-frequency electric power source circuit inaccordance with the increase rate in a second period following the firstperiod; acquiring, by the control circuit, the value relating to theimpedance of the biological tissue in the second period; andterminating, by the control circuit, the second period after the valuerelating to the impedance reaches a minimum value.

According to an aspect of the invention, an electric power source devicefor operating a high-frequency treatment instrument is configured toperform a high-frequency treatment on a biological tissue. The deviceincludes a high-frequency electric power source circuit configured tooutput electric power; an output detection circuit configured to detectthe output; and a control circuit configured to acquire a value relatingto the output from the output detection circuit, and configured tocontrol an operation of the high-frequency electric power sourcecircuit. The control circuit being configured to execute causing thehigh-frequency electric power source circuit to output the electricpower; acquiring, based on the value relating to the output acquiredfrom the output detection circuit, an initial impedance value, which isa value relating to an impedance of the biological tissue, in a firstperiod from a start of the output; determining an increase rate of anoutput voltage relative to time, based on the initial impedance value;increasing the output voltage of the high-frequency electric powersource circuit in accordance with the increase rate in a second periodfollowing the first period; acquiring the value relating to theimpedance of the biological tissue in the second period; and terminatingthe second period after the value relating to the impedance reaches aminimum value.

According to an aspect of the invention, a high-frequency treatmentsystem includes the above-mentioned electric power source device; andthe high-frequency treatment instrument.

Advantages of the invention will he set forth in the description whichfollows, and in part will be obvious from the description, or may helearned by practice of the invention. The advantages of the inventionmay be realized and obtained by means of the instrumentalities andcombinations particularly pointed out hereinafter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention, andtogether with the general description given above and the detaileddescription of the embodiments given below, serve to explain theprinciples of the invention.

FIG. 1 is a view which schematically illustrates an example of theexternal appearance of a high-frequency treatment system according to anembodiment.

FIG. 2 is a block diagram which schematically illustrates aconfiguration example of the high-frequency treatment system accordingto the embodiment.

FIG. 3 is a flowchart illustrating an example of the operation of thehigh-frequency treatment system according to the embodiment.

FIG. 4 shows an example of variations of an electric power, a voltage, acurrent and an impedance relative to time in the high-frequencytreatment system according to the embodiment.

FIG. 5 is a flowchart illustrating an example of first control of thehigh-frequency treatment system according to the embodiment.

FIG. 6 shows an example of the relationship between duration ofapplication of a voltage to a biological tissue in second control and avessel burst pressure of a blood vessel which is sealed by thetreatment.

FIG. 7 is a flowchart illustrating an example of the second control ofthe high-frequency treatment system according to the embodiment.

FIG. 8 shows at example of a table including a relationship between aninitial resistance value and an additional resistance value, which areused in the high-frequency treatment system according to the embodiment.

FIG. 9 shows an example of a table including a relationship between aninitial resistance value, duration and an additional resistance value,which are used in the high-frequency treatment system according to theembodiment.

FIG. 10 shows an example of a graph of a target resistance value versustime in the high-frequency treatment system according to the embodiment.

FIG. 11 shows an example of a graph of an output electric power and aresistance value versus time in the high-frequency treatment systemaccording to the embodiment.

FIG. 12 is a flowchart illustrating an example of third control of thehigh-frequency treatment system according to the embodiment.

DETAILED DESCRIPTION OF THE INVENTION

An embodiment of the present invention will be described hereinafterwith reference to the accompanying drawings. FIG. 1 is a schematic viewof a high-frequency treatment system 10 according to the presentembodiment. As illustrated in this Figure, the high-frequency treatmentsystem 10 includes a high-frequency treatment instrument 100 whichfunctions as a high-frequency treatment instrument, an electric powersource device 200 which supplies electric power to the treatmentinstrument, and a footswitch 290.

The high-frequency treatment instrument 100 includes a treatment portion110, a shaft 160, and an operation. portion 170. For the purpose ofdescriptions below, the treatment portion 110 side is referred to as adistal side, and the operation portion 170 side is referred to as aproximal side. The high-frequency treatment system 10 is configured tograsp a biological tissue, such as a blood vessel, which is a treatmenttarget, by the treatment portion 110. The high-frequency treatmentsystem 10 applies a high-frequency voltage to the grasped biologicaltissue, thereby sealing this biological tissue.

The treatment portion 110, which is provided at a distal end of theshaft 160, is provided with a first grasping member 112 and a secondgrasping member 114, which are a pair of grasping members. Those partsof the first grasping member 112 and second grasping member 114, whichcome in contact with the biological tissue, function as electrodes,respectively. Specifically, the first grasping member 112 and secondgrasping member 114 function as bipolar electrodes.

The operation portion 170 is provided an operation portion main body172, a stationary handle 174, a movable handle 176, and an output switch178. The stationary handle 174 is fixed to the operation portion mainbody 172, and the movable handle 176 is displaced relative to theoperation portion main body 172. The movable handle 176 is connected toa wire or a rod, which is inserted through the shaft 160. This wire orrod is connected to the second grasping member 114 The movement of themovable handle 176 is transmitted to the second grasping member 114. Thesecond grasping member 114 is displaced relative to the first graspingmember 112 in accordance with the movement of the movable handle 176. Asa result, the first grasping member 112 and second grasping member 114open or close relative to each other.

The output switch 178 includes, for example, two buttons. These buttonsare buttons which are pressed when high-frequency electric power is madeto act on the biological tissue, which is the treatment target, by thetreatment portion 110. The electric power source device 200, whichdetects the pressing of the button, applies a high-frequency voltagebetween the first grasping member 112 and second grasping member 114. Asa result, the biological tissue, which is grasped by the treatmentportion 110, is sealed. The high-frequency treatment instrument 100 isconfigured, for example, such that the output level varies depending onwhich of the two buttons is pressed. The footswitch 290 is also providedwith, for example, two switches. The two respective switches of thefootswitch 290 have the same functions as the respective buttons of theoutput switch 178. The high-frequency treatment system 10 may beprovided with both the output switch 178 and the footswitch 290, or maybe provided with one of them. hereinafter; a description will be givenon the assumption that the output switch 178 is mainly operated, but thefootswitch 290 may be operated.

One end of a cable 180 is connected to the proximal side of theoperation portion 170. The other end of the cable 180 is connected tothe electric power source device 200. The electric power source device200 controls the operation of the high-frequency treatment instrument100, and supplies electric power to the high-frequency treatmentinstrument 100.

FIG. 2 is a block diagram which schematically illustrates aconfiguration example of the electric power source device 200. Theelectric power source device 200 includes a control circuit 210, ahigh-frequency electric power source circuit 220, an output detectioncircuit 230, an A/D converter 240, a storage medium 250, an input device262, a display 264, and a speaker 266.

The control circuit 210 includes an integrated circuit or the like, suchas a central processing unit (CPU), an application specific integratedcircuit (ASIC), or a field programmable gate array (FPGA). The controlcircuit 210 may be composed of a single integrated circuit or the like,or may be composed of a combination of a plurality of integratedcircuits or the like. The operation of the control circuit 210 isexecuted, for example, in accordance with a program stored in thecontrol circuit 210 or in the storage medium 250. The control circuit210 acquires information from each component of the electric powersource device 200, and controls the operation of each component.

The high-frequency electric power source circuit 220 outputshigh-frequency electric power which is supplied to the high-frequencytreatment instrument 100. The high-frequency electric power sourcecircuit 220 includes a variable DC electric power source 221, a waveformgenerating circuit 222, and an output circuit 223. The variable DCelectric power source 221 outputs DC electric power under the control ofthe control circuit 210. The output of the variable DC electric powersource 221 is transmitted to the output circuit 223. The waveformgenerating circuit 222 generates an AC waveform under the control of thecontrol circuit 210, and outputs the generated AC waveform. The outputof the waveform generating circuit 222 is transmitted to the outputcircuit 223. The output circuit 223 superimposes the output of thevariable DC electric power source 221 and the output of the waveformgenerating circuit 222, and outputs AC electric power. This AC electricDower is supplied, via the output detection circuit 230, to the firstgrasping member 112 and second grasping member 114 of the high-frequencytreatment instrument 100.

The output detection circuit 230 includes a current detection circuit231 and a voltage detection circuit 232. The current detection circuit231 is inserted in a circuit from the high-frequency electric powersource circuit 220 to the high-frequency treatment instrument 100, andoutputs an analog signal which represents a current value that is outputfrom the high-frequency electric power source circuit 220. The voltagedetection circuit 232 outputs an analog signal which represents anoutput voltage of the high-frequency electric power source circuit 220.

The output signal of the current detection circuit 231 and the outputsignal of the voltage detection circuit 232 are input to the A/Dconverter 240. The A/D converter 240 converts the input analog signalsto a digital signal, and sends the digital signal to the control circuit210. In this manner, the control circuit 210 acquires information of theoutput voltage and output current of the high-frequency electric powersource circuit 220. In addition, based on the output voltage and outputcurrent, the control circuit 210 calculates a value relating to animpedance of a circuit including the first grasping member 112, thebiological tissue that is the treatment target, and the second graspingmember 114. Specifically, the control circuit 210 acquires a valuerelating to the impedance of the biological tissue.

The storage medium 250 stores programs which are used in the controlcircuit 210, and various parameters, tables, etc. which are used incalculations executed in the control circuit 210.

The input device 262 includes an input device such as a button, aslider, a dial, a keyboard, or a touch panel The control circuit 210acquires an input to the input device 262 by the user. The display 264includes a display device such as a liquid crystal display or an LEDlamp. The display 264 presents information relating to thehigh-frequency treatment system 10 to the user, under the control of thecontrol circuit 210. The speaker 266 issues, for example, an inputsound, an output sound, an alarm sound, etc., under the control of thecontrol circuit 210.

The operation of the high-frequency treatment system 10 according to thepresent embodiment will be described.

The user operates the input device 262 of the electric power sourcedevice 200, and sets a desired output level for the high-frequencytreatment instrument 100. The output level is set, for example, for eachof the plural output switches 178.

The treatment portion 110 and shaft 160 are inserted, for example, intoa peritoneal cavity through an abdominal wall. The user opens or closesthe treatment portion 110 by operating the movable handle 176. In thismanner, the first grasping member 112 and second grasping member 114grasp the biological tissue that is the treatment target. When thebiological tissue is grasped by the treatment portion 110, the useroperates the output switch 178. The control circuit 210 of the electricpower source device 200, which detected the pressing of the button ofthe output switch 178, outputs an instruction, which relates to driving,to the high-frequency electric power source circuit 220,

The high-frequency electric power source circuit 220 applies, under thecontrol of the control circuit 210, a high-frequency voltage to thefirst grasping member 112 and second grasping member 114 of thetreatment portion 110, and causes a high-frequency current to flowthrough the biological tissue that is the treatment target. If thehigh-frequency current flows, the biological tissue becomes anelectrical resistance. Thus, heat is generated in the biological tissue,and the temperature of the biological tissue rises. As a result, theprotein of the biological tissue is denatured, and the biological tissueis sealed. By the above, the treatment of the biological tissue iscompleted.

The output operation of the electric power source device 200 will bedescribed in detail. The outline of the operation of the electric powersource device 200 according to the present embodiment will be describedwith reference to a flowchart of FIG. 3. In step S101, the controlcircuit 210 determines whether the output switch 178 is turned on. Ifthe output switch 178 is not turned on, the process returns to stepS101. In other words, the control circuit 210 stands by until the outputswitch 178 is turned on. When the output switch 178 is turned on, theprocess advances to step S102. In step S102, the control circuit 210executes first control. Then, in step S103, the control circuit 210executes second control. Subsequently, in step S104, the control circuit210 executes third control. The first control, second control and thirdcontrol will he described later in detail. By the above, the outputcontrol is terminated. In this manner, in the present embodiment,three-stage controls are executed.

Referring to FIG. 4, a description is given of an example of an outputof the high-frequency treatment system 10 according to the embodiment,and an impedance relating to the biological tissue, which is calculatedat the time of the output. In FIG. 4, the horizontal axis indicatestime, which is set such that an output start time is 0. The leftvertical axis indicates an output electric power, an output voltage, andan output current. The right vertical axis indicates an impedance. InFIG. 4, a solid line indicates a variation of the output voltage, adashed line indicates a variation of the impedance, a dashed-dotted lineindicates a variation of the output electric power, and a dasheddouble-dotted line indicates a variation of the output current.

As described above, the control of the output of the high-frequencytreatment system 10 according to the present embodiment is divided intothree stages (three phases). Accordingly, the period, during whichelectric power is supplied to the biological tissue, includes a firstperiod in which the first control of a short period immediately afterthe output start is executed, a subsequent second period in which thesecond control of about one second is executed, and a subsequent thirdperiod in which the third control of about two seconds is executed. Theoutput by the first control is referred to as a first output, the outputby the second control is referred to as a second output, and the outputby the third control is referred to as a third output. In addition,since the output by the second control is executed prior to the outputby the third control, the period by the second control is referred to asa former period, and the period by the third control is referred to as alatter period.

In the first control, high-frequency electric power having apredetermined electric power value is supplied to the biological tissueduring a predetermined period. This first period is, for example, about100 milliseconds. During the first period, the value relating to theimpedance is acquired. In accordance with the size, kind, etc. of thebiological tissue that is the treatment target, or the state of thebiological tissue, the value relating to the impedance, which isacquired at that time, will vary. Thus, in the present embodiment, basedon the value relating to the impedance which is acquired in the firstperiod in which the first control is executed, the state of thebiological tissue that is the treatment target is ascertained, andcontrol parameters, which are used in the subsequent control, aredetermined. Specifically, the control parameters, which correspond tothe characteristics of the biological tissue that is the treatmenttarget, are set. In addition, in the first control, an overshoot of theoutput is suppressed by a predetermined electric power, which is not solarge, being supplied to the biological tissue.

In the second control, a voltage which increases linearly is applied tothe biological tissue. The temperature of the biological tissue rises inthe second period in which the second control is executed. The secondcontrol is executed until it is detected that the value relating to themeasured impedance takes a minimum value. If the value relating to themeasured impedance takes the minimum value, the control transitions tothe third control.

If moisture evaporates in the second control, the value relating to theimpedance increases subsequently in accordance with the rise intemperature. In the third control, the output control is executed suchthat the value relating to the impedance increases linearly. In thisthird period, the temperature of the biological tissue is keptsubstantially constant.

Hereinafter, the first to third controls will be described in detail.

[First Control]

The first control will be described with reference to a flowchartillustrated in FIG. 5.

In step S201, the control circuit 210 causes the high-frequency electricpower source circuit 220 to supply AC electric power having apredetermined electric power value to the biological tissue that is thetreatment target, which is clamped between the first grasping member 112and second grasping member 114. By the supply of the AC electric power,an AC current flows through the biological tissue.

In step S202, the control circuit 210 acquires an impedance valuerelating to the biological tissue that is the treatment target. Forexample, the control circuit 210 acquires the current detected by thecurrent detection circuit 231 of the output detection circuit 230, andthe voltage detected by the voltage detection circuit 232 of the outputdetection circuit 230, and calculates the impedance value based on thesevalues. Here, the calculated impedance value may be various kinds ofvalues relating to the impedance, and may be, for example, an absolutevalue of the impedance which is a complex number, or may be a resistancevalue which is a real number component of the impedance. An admittance,which is a reciprocal of the impedance, may be used.

In step S203, the control circuit 210 determines whether a predeterminedtime has passed. Here, the predetermined time is, for example, 100milliseconds. If the predetermined time has not passed, the processreturns to step S201. Specifically, the supply of the predeterminedelectric power and the acquisition of the impedance value are repeated.When the predetermined time has passed, the first control ends, and atransition occurs to the second control.

The impedance value, which is acquired in the first control, is referredto as an initial impedance value. The impedance value may be animpedance value which is first acquired, or may be a mean value or amedian of impedance values acquired in some periods in the first periodduring which the first control is executed.

[Second Control]

The second control will be described in detail. The second control is acontrol which is optimized in order to stably seal a blood vessel or thelike. Here, attention is paid to a change of the impedance value at atime when the biological tissue such as a blood vessel, is heated. Ifthe biological tissue is heated, the temperature of an electrolytesolution in the biological tissue rises, and the impedance decreases.Paying attention to this decrease of the impedance, the following becameclear.

FIG. 6 illustrates the relationship between duration of a voltageapplication (heating time) by the second control and a mean value of avessel burst pressure (VBP). Here, the duration of the voltageapplication by the second control is a time from when the second controlstarted until when the impedance value takes the minimum value, asdescribed above. In addition, as described above and as illustrated inFIG. 4, the second control is a control in which the output voltage isadjusted so as to increases linearly. The VBP indicates a pressure atwhich a sealed part is peeled when a water pressure is applied to theblood vessel after the seal treatment through the second control andthird control. Specifically, as the VBP becomes higher, this means thatstronger sealing is performed. In general, it is required that a VBP of360 mmHg or above be obtained in the blood vessel after at least 90% ormore of the treatment. As illustrated in FIG. 6, the VBP tends toincrease, as the time until the impedance value takes the minimum valuebecomes longer. In addition, even when the time until the impedancevalue takes the minimum value increased to one second or more, the VBPdid not increase so much.

Taking into account the result shown in FIG. 6 and the fact that ashorter treatment time is desired, it is considered that the time untilthe impedance value takes the minimum value should preferably be aboutone second. It is understood that the time may be in a range of betweenabout 0.5 seconds and 1.5 seconds, in which the VBP is sufficientlyhigher than 360 mmHg. In consideration of these results, in the presentembodiment, the output voltage in the second control is adjusted suchthat the time until the impedance value takes the minimum value becomesabout one second.

In the present embodiment, the control circuit 210 controls the outputvoltage V(t) which is applied to the biological tissue in the secondcontrol, as indicated by the following equation (1):

V(t)=(V(Z)/GV)×t   (1)

where t is a time from the start of treatment, that is, a time from thestart of the first control. The time t may be a time from the start ofthe second control. V(Z) is a constant, for example, a maximum value ofthe output voltage. GV is a gradient value. Thus, (V(Z)/GV) indicates anincrease value of the output voltage per unit time, that is, aninclination (increase rate).

GV is determined based on the initial impedance value acquired in thefirst control. For example, based on an initial resistance value R0, GVis determined by the following equation (2):

GV=a·R0+b,   (2)

where a and b are fixed values. The values a and b are empiricallyadjusted such that the impedance value takes the minimum value in aboutone second, when the output voltage V(t) is applied to the biologicaltissue.

The above equation (2) is not limited to an equation of a linearfunction, and may be another equation such as a function of a higherdegree. However, the linear function is preferable to a higher-degreefunction, so that the influence, which the initial resistance value R0exerts on the above equation (1), may not become excessively large Inaddition, the above equation (1) is also a linear function relating totime. Because of the linear function, a proper temperature rise withhigh stability can be obtained. Since the output voltage is the linearfunction relating to time, the electric power, which is input to thebiological tissue, increases in a manner of a quadratic function withrespect to time. An offset may be added to the output voltage V(t).Specifically, the above equation (1) may be modified as follows:

V(t)=(V(Z)/GV)×t+c,   (3)

where c is a fixed value.

According to the above equations (1) and (2), for example, in a thinblood vessel, the initial resistance value RD is relatively high. Thus,(V(Z)/GV), which indicates a gradient, is relatively small.Specifically, in a thin blood vessel, the output voltage increasesrelatively slowly, and accordingly the input electric power increasesrelatively slowly. On the other hand, for example, in a thick bloodvessel, the initial resistance value RD is relatively low. Thus,(V(Z)/GV), which indicates the gradient, is relatively large.Specifically, in a thick blood vessel, the output voltage increasesrelatively quickly, and accordingly the input electric power increasesrelatively quickly.

The gradient (V(Z)/GV) may be calculated at each time and used, based onthe relationships of the above equations (1) and (2) and the initialresistance value R0, or may be determined based on the table prestoredin the storage medium 250, which represents the relationship between theinitial resistance value R0 and gradient (V(Z)/GV), and based on theinitial resistance value.

The operation of the electric power source device 200 in the secondcontrol will be described with reference to a flowchart of FIG. 7.

In step S301, the control circuit 210 calculates the relationshipbetween time and output voltage V(t), based on the initial impedancevalue. The output voltage V(t) is determined, for example, by using theabove equations (1) and (2).

In step S302, the control circuit 210 causes the high-frequency electricpower source circuit 220 to output the voltage V(t) which corresponds totime. In step S303, the control circuit 210 acquires the impedance valueof the biological tissue.

In step S304, the control circuit 210 determines whether the impedancevalue acquired in step S303 is a change-over impedance value or not.Here, the change-over impedance value is an impedance value which is acondition for terminating the second control. The change-over impedancevalue can be, for example, a value at a time when the variation of theimpedance value is measured and the impedance value becomes the minimumvalue. In order to easily detect the minimum value, a value, which hasincreased by a predetermined value after the impedance value took theminimum value, may be set as the change-over impedance value.Specifically, in step S304, when the impedance value decreased and tookthe minimum value and then the impedance value has increased by thepredetermined value, it may he determined that the impedance value hasbecome the change-over impedance value. In step S304, when it isdetermined that the impedance value is not the change-over impedancevalue, the process returns to step S302. On the other hand, when it isdetermined that the impedance value is the change-over impedance value,the second control is terminated, and a transition occurs to the thirdcontrol.

By the above-described controls, the output voltage and the impedancevalue become as illustrated in FIG. 4. Specifically, in the secondperiod in which the second control is executed, the output voltageincreases linearly At this time, the output electric power increases ina manner of a quadratic function. The impedance value acquired in thesecond period decreases slowly with time. In the example illustrated inFIG. 4, when the impedance value has slightly increased after taking theminimum value, the second control is terminated. In the meantime,although the example in which the output voltage is controlled isillustrated here, the output current or output electric power may becontrolled so as to increase linearly in the same manner.

The time until the impedance value takes the minimum value is set to beabout one second and is relatively slow. It is thus possible to makeuniform the temperature of the biological tissue, while shortening thetime of the treatment. In addition, by setting the time until theimpedance value takes the minimum value to be constant at about onesecond, regardless of the size, etc. of the treatment target, it ispossible to suppress a variance in results of treatments. In themeantime, when the same energy is input, the impedance value takes theminimum value in a shorter time, as the thickness of the blood vesselbecomes smaller. By setting the time until the impedance value takes theminimum value to be about one second, a high sealing strength can beobtained stably, as illustrated in FIG. 6.

[Third Control]The third control will be described in detail. In thethird control, the output is controlled such that the measured impedancevalue increases with a constant rate. In the present embodiment, a stopimpedance value, which is an impedance value at a time when the outputis stopped, is first determined. Next, target impedance which increasesat a constant speed from the impedance value at the start time of thethird control up to the stop impedance value is set. Specifically, thetarget impedance value is set as a target value of the impedance valueat each time. The control of the output is executed such that the outputvalue is determined at predetermined time intervals, based on adifference between the target impedance value and a measured impedancevalue acquired by using the output detection circuit 230. In thismanner, the third control is executed until the measured impedance valuereaches the stop impedance value along target impedance values.

<Setting of the Stop Impedance Value in the Third Control>

A determination method of the stop impedance value at. the time ofstopping the output will be described. Here, a description is given ofthe case of using a resistance value as the impedance value. The sameapplies to cases using other impedance values, aside from the resistancevalue. A stop resistance value Rstop, which is a resistance value at thetime of stopping the output, is calculated by, for example, thefollowing equation (4):

Rstop=Rin+Radd.   (4)

Rin is a resistance value relating to the biological tissue, which isacquired at the start time of the third control. Specifically, Rin isthe resistance value corresponding to the above-described change-overimpedance value. The Rin may be the minimum impedance measured in thesecond control. In addition, the initial impedance value acquired in thefirst control may be used for Rin.

Radd is an additional resistance value which is determined based oninitial state of the biological tissue. Some examples of thedetermination method of the additional resistance value Radd will beillustrated.

First Example

The additional resistance value Radd is calculated as a function of theinitial resistance value R0. The initial resistance value R0 is theresistance value detected in the first control. The storage medium 250stores a table, for example, as illustrated in FIG. 8, the tablerepresenting the relationship between the additional resistance valueRadd and initial resistance value R0. Based on this table and theinitial resistance value R0 measured in the first control, theadditional resistance value Radd is determined.

In FIG. 8, a, b, c and d represent resistance values, and have arelationship of a<b<c<d. Specifically, as the initial resistance valueR0 becomes higher, the additional resistance value Radd becomes lower.In other words, when the treatment target is a blood vessel, a thinnerblood vessel has a higher initial resistance R0, and thus the additionalresistance value Radd becomes lower. In addition, the additionalresistance value Radd may be calculated based on a function representingthe same relationship as in FIG. 8.

Second Example

The additional resistance value Radd is calculated as a function of theinitial resistance value R0 and duration Dt of the second control. Theduration Dt is acquired when the second control is finished. Forexample, when the initial resistance value R0 is a predeterminedthreshold value or more, and when the duration Dt is a predeterminedthreshold value or less, a first additional resistance value Radd1 isselected as the additional resistance value Radd. When the initialresistance value R0 is lower than the predetermined threshold value, orwhen the duration Dt is longer than the predetermined threshold value, asecond additional resistance value Radd2 is selected as the additionalresistance value Radd. Here, the first additional resistance value Radd1is lower than the second additional resistance value Radd2.

In addition, the storage medium 250 stores a table, for example, asillustrated in FIG. 9, the table representing the relationship betweenthe additional resistance value Radd, duration Dt and initial resistancevalue R0. Based on this table, the initial resistance value R0 measuredin the first control and the duration Dt of the second control, theadditional resistance value Radd may be determined. In FIG, 9, a, b, cand d represent resistance values, and have a relationship of a<b<c<d.Specifically, as the initial resistance value R0 becomes higher, theadditional resistance value Radd becomes lower; and as the duration Dtbecomes longer, the additional resistance value Radd becomes higher. Inaddition, the additional resistance value Radd may be calculated basedon a function representing the same relationship as in FIG. 9.

Based on the initial resistance value R0 and the duration Dt of thesecond control, the additional resistance value Radd is determined.Thereby, a more appropriate additional resistance value Radd can bedetermined than in the case in which the additional resistance valueRadd is determined based on only the initial resistance value RD.

Third Example

The additional resistance value Radd may be selected in accordance withan output level which the user sets. For example, as the output levelbecomes higher, the additional resistance value Radd becomes higher; andas the output level becomes lower, the additional resistance value Raddbecomes lower. It is preferable that, like the case of the first exampleor the second example, the output level is used in combination with theinitial resistance value R0 or the duration Dt of the second control. Amore appropriate value can be set, by the additional resistance valueRadd being determined by using the output level in combination with theinitial resistance value R0 or the duration Dt of the second control.

In each of the above first to third examples, for instance, as the bloodvessel becomes thinner, the additional resistance value Radd becomeslower; and as the blood vessel becomes thicker, the additionalresistance value Radd becomes higher. The stop resistance value Rstop ishigher than the initial resistance value R0.

Like the above, when a value relating to the impedance, other than theresistance value, is used, Rin corresponds to the change-over impedancevalue, the additional resistance value Radd corresponds to theadditional impedance value, and the initial resistance value R0corresponds to the initial impedance value.

As described above, use is made of the initial impedance value whichvaries in accordance with the treatment target, for instance, thethickness of the blood vessel. Thereby, the stop impedance valuecorresponding to the treatment target is appropriately set. Since theoutput control is executed by using the thus determined stop impedancevalue, a proper treatment can be performed.

<Setting of the Target Impedance Value in the Third Control>

A setting method of the target impedance value will be described. Here,a description is given of the case in which, like the above-describedstop resistance value, the resistance value is used as the impedancevalue. Specifically, the case in which a target resistance value is usedas the target impedance value will be described. The same applies to thecases of using other values relating to the impedance, aside from theresistance value.

First Example

In a first example, a time in which high-frequency electric power isoutput by the third control predetermined. A target resistance value ateach time can be set such that, in this predetermined time, theresistance value linearly increases up to the stop resistance valueRstop which is calculated from the change-over resistance value Rin.

Second Example

In a second example, a time in which high-frequency electric power isoutput by the third control is determined in accordance with the outputlevel that is set by the user. A target resistance value can be set suchthat, in the time determined in accordance with the output level, theresistance value linearly increases up to the calculated stop resistancevalue Rstop. Specifically, as illustrated in FIG. 10, an inclination ata time when the target resistance value is indicated relative to timevaries in accordance with the output level. In other words, the speed ofincrease of the target resistance value varies in accordance with theoutput level. In FIG. 10, L1, L2 and L3 indicate output levels, and havea relationship of L1<L2<L3.

Third Example

In a third example, a time in which high-frequency electric power isoutput by the third control is determined in accordance with theresistance value (initial resistance value) acquired in the firstcontrol. In addition, the time in which high-frequency electric power isoutput by the third control may be determined in accordance with theresistance value acquired in the second control. A target resistancevalue can be set such that, in the determined time, the resistance valuelinearly increases up to the calculated stop resistance value Rstop.Specifically, an inclination at a time when the target resistance valueis indicated relative to time varies in accordance with the resistancevalue acquired in the first control or second control. In other words,the speed of increase of the target resistance value varies inaccordance with the resistance value acquired in the first control orsecond control. For example, when the resistance value acquired in thefirst control or second control is low, the output time in the thirdcontrol becomes shorter and the inclination becomes larger. On the otherhand, when the resistance value acquired in the first control or secondcontrol is high, the output time in the third control becomes longer andthe inclination becomes smaller.

<Determination Method of Output Electric Power in the Third Control>

A determination method of an output will be described. Like theabove-described case, the case in which a resistance value is used asthe impedance value is described. The same applies to the cases of usingother values relating to the impedance, aside from the resistance value.

A description will be given with reference to FIG. 11.

An upper part of FIG. 11 schematically illustrates a target resistancevalue and a measured resistance value relative to time. Here, the targetresistance value is indicated by a broken line, and the measuredresistance value is indicated by a solid line. A lower part of FIG. 11schematically illustrates output electric power relative to time. In thepresent embodiment, the output electric power is set in each step timeof several-ten milliseconds. The setting of the output electric power isexecuted by comparing the target resistance value and the measuredresistance value. Specifically, the target resistance value and themeasured resistance value are compared at predetermined time intervals.When the measured resistance value is higher than the target resistancevalue, the output electric power is decreased. On the other hand, whenthe measured resistance value is lower than the target resistance value,the output electric power is increased. In addition, when the differencebetween the measured resistance value and the target resistance value isless than a predetermined threshold value, the output electric power ismaintained. The output electric power at the start time of the thirdcontrol may be the output electric power at the end time of the secondcontrol. The output electric power at the start time of the thirdcontrol may be a predetermined value, or may be determined by apredetermined method.

If the set value of the output electric power is frequently changed,there is concern that the output oscillates. On the other hand, if thesetting of the output electric power is executed only occasionally, theprecision in control would lower, or the treatment could not becompleted within a target time. Thus, it is preferable that the intervalof re-setting of output electric power, that is, the step time, isappropriately adjusted. Examples of the determination method of theoutput electric power will be described.

First Example

In a first example, a change amount of the output electric power is apredetermined ratio relative to the output electric power at that timepoint. For example, this predetermined ratio is set as a first ratio. Inthis case, when the initial output electric power a first electricpower, and the measured resistance value is higher than the targetresistance value, the next output electric power is set at a secondelectric power which is lowered from the first electric power by thefirst ratio. When the output is a second electric power, and themeasured resistance value is lower than the target resistance value, thenext output electric power is set at a third electric power which israised from the second electric power by the first ratio. Subsequently,the output electric power is controlled in the same manner. For example,if the first ratio is set at 10%, the output electric power iscontrolled as follows. When the output electric power is 20 W at thattime point and the measured resistance value is higher than the targetresistance value, the next output electric power is adjusted at 18 W.When the output electric power is 18 W and the measured resistance valueis lower than the target resistance value, the next output electricpower is adjusted at 19.8 W. By setting the change amount of the outputelectric power to be the predetermined ratio relative to the outputelectric power at that time point, the change amount is adjusted to aproper value at each of a time when the output electric power is largeand a time when the output electric power is small. The numerical valuesillustrated here are merely examples, and any numerical value can beused for the proper setting

In the meantime, when the ratio at the time of lowering the outputelectric power is set as a first ratio and the ratio at the time ofraising the output electric power is set as a second ratio, the firstratio and the second ratio may be equal or different. It is preferablethat the first ratio is greater than the second ratio. For example, whenthe measured resistance value is higher than the target resistancevalue, the output is lowered by 10%. When the measured resistance valueis lower than the target resistance value, the output is raised by 5%.In addition, when the difference between the measured resistance valueand the target resistance value is within a predetermined range, theoutput electric power may not be changed.

Second Example

In a second example, a change amount of the output electric power is apredetermined value. In a case in which this predetermined ratio is setas a first value, when the measured resistance value is higher than thetarget resistance value, the next output electric power is adjusted at avalue which is lowered from the present output electric power by a firstvalue. When the measured resistance value is lower than the targetresistance value, the next output electric power is adjusted at a valuewhich is higher than the present output electric power by the firstvalue. For example, when the change amount is set to be 2 W, the outputelectric power is controlled as follows. When the output electric poweris 20 W at that time point and the measured resistance value is higherthan the target resistance value, the next output electric power isadjusted at 18 W. When the output electric power is 18 W and themeasured resistance value is lower than the target resistance value, thenext output electric power is adjusted at 20 W. By setting the changeamount of the output electric power at a constant value, the hardwareconfiguration becomes simpler, and the control of the output electricpower becomes easier. The numerical values illustrated here are merelyexamples, and any numerical value can he used for the proper setting.

In the meantime, the change amount at the time of raising the output andthe change amount at the time of lowering the output may be equal ordifferent. It is preferable that the change amount at the time oflowering the output is greater than the change amount at the time ofraising the output. In addition, when the difference between themeasured resistance value and the target resistance value is within apredetermined range, the output electric power may not be changed.

Third Example

In a third example, a change amount of the output electric power isdetermined based on the initial resistance value R0 acquired in thefirst control, and the length of the second period in which the secondcontrol is executed, that is, the period from when the second controlstarted until when the impedance values takes the minimum value. Thus,the storage medium 250 prestores, for example, a relationship betweenthe initial resistance value R0, the length of the second period, andthe change amount of the output electric power. The control circuit 210determines the output electric power by referring to this relationship.

Fourth Example

In a fourth example, a change amount of the output electric power is apredetermined value which is determined in accordance with an outputlevel that is set by the user. The storage medium 250 prestores arelationship between the output level and the change amount of theoutput electric power. The control circuit 210 determines the outputelectric power by referring to this relationship.

Fifth Example

In a fifth example, the output electric power is determined by therelationship between the measured. resistance value and the targetresistance value. For example, the output electric power is set asfollows. When the measured resistance value is higher than the targetresistance value, the output electric power is set at a first electricpower value. When the measured resistance value is equal to the targetresistance value, the output electric power is set at a second electricpower value. When the measured resistance value is lower than the targetresistance value, the output electric power is set at a third electricpower value. Here, the electric power values become greater in the orderof the first electric power value, second electric power value and thirdelectric power value. For example, the first electric power value is 5W, second electric power value is 8 W, and third electric power value is10 W. The numerical values illustrated here are merely examples, and anynumerical value can be used for the proper setting.

The third control, which is controlled in the above manner, will bedescribed with reference to a flowchart of FIG. 12.

In step S401, the control circuit 210 calculates the additionalimpedance value, based on the initial impedance value. In step S402, thecontrol circuit 210 sets the stop impedance value, based on the sum ofthe change-over impedance value and the additional impedance value. Forexample, any of the methods of the above-described first to thirdexamples may be used for the setting method of the stop impedance value.

In step S403, the control circuit 210 sets the target impedance value byusing the stop impedance value. Any of the methods of theabove-described first to third examples may be used for the settingmethod of the target impedance value. In step S404, the control circuit210 causes the high-frequency electric power source circuit 220 tooutput, as an initial electric power, the electric power having apredetermined electric power value. The initial electric power is, forexample, the electric power at the time of the end of the secondcontrol.

In step S405, the control circuit 210 acquires the impedance value byusing the value detected by the output detection circuit 230. In stepS406, the control circuit 210 determines whether the measured impedancevalue is the stop impedance value or more. When the measured impedancevalue is not the stop impedance value or more, the process advances tostep S407.

In step S407, the control circuit 210 compares the measured impedancevalue (Zm) and the target impedance value (Zt). When the differencebetween the measured impedance value (Zm) and the target impedance value(Zt) is within a predetermined threshold value (Zm≈Zt), the processadvances to step S408. In step S408, the control circuit 210 maintainsthe set value (set electric power) of the output electric power.Thereafter, the process advances to step S411. In step S407, when it isdetermined that the measured impedance value (Zm) is greater than thetarget impedance value (Zt) (Zm>Zt), the process advances to step S409.In step S409, the control circuit 210 sets the set electric power to alow electric power. Then, the process advances to step S411. In stepS407, when it is determined that the measured impedance value (Zm) isless than the target impedance value (Zt) (Zm<Zt), the process advancesto step S410. In step S410, the control circuit 210 sets the setelectric power to a high electric power. Then, the process advances tostep S411. For example, any of the methods of the above-described firstto fifth examples may be used for the method of setting the electricpower in each of step S408 to step S410.

In step S411, the control circuit 210 causes the high-frequency electricpower source circuit 220 to output the electric power of the electricpower value which is set in any one of steps S408 to step S410.Thereafter, the process returns to step S405.

In step S406, when it is determined that the measured impedance is thestop impedance value or more, the process advances to step S412. In stepS412, the control circuit 210 causes the high-frequency electric powersource circuit 220 to stop the output. Then, the third control isfinished. By the above, the supply of the high-frequency electric powerto the high-frequency treatment instrument 100 by the electric powersource device 200 is terminated.

According to the above-described control, the output and the acquiredimpedance value are as illustrated in FIG. 4. Specifically, in the thirdcontrol, the impedance value increases linearly. The output electricpower (output voltage or output current) is adjusted such that theimpedance value increases linearly.

According to the above-described third control, the impedance valueincreases linearly, and thus the temperature of the biological tissue iskept substantially constant. In this manner, the treatment of thebiological tissue progresses at substantially constant temperatures.Thus, for example, the stable sealing of the blood vessel can beobtained.

In addition, since the stop impedance value, which corresponds to thecharacteristics of the biological tissue, is determined, the conditionfor finishing the treatment, which corresponds to the characteristics ofthe biological tissue, is determined. Specifically, the treatment isfinished at a time point when sufficient treatment is conducted,regardless of differences in characteristics of biological tissues whichare treatment targets.

As described above, according to the present embodiment, in thehigh-frequency treatment system 10, the output, which is optimized inaccordance with the treatment target, can be executed.

The above description of the embodiment is given by taking, mainly, thesealing of the blood vessel as an example. However, the above-describedtechnique applicable to treatments of other biological tissues. Inaddition, the above-described operation may be prepared as a mode forsealing a blood vessel, and this mode may be prepared as well as othermodes in the high-frequency treatment system 10. The high-frequencytreatment system 10 may be configured such that the user can select amode corresponding to a treatment, from among these modes.

The high-frequency treatment system 10 according to the presentembodiment may be configured not only to output the high-frequencyelectric power, but also to have a function as an ultrasonic treatmentinstrument, which treats a biological tissue by ultrasonic vibration,for example, by the first grasping member 112 vibrating at an ultrasonicfrequency. A treatment instrument, which also uses ultrasonic energy,can function in the same manner as in the above-described embodimentwith respect to the output of the high-frequency electric power.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

1. An operation method of an electric power source device for operatinga high-frequency treatment instrument configured to perform ahigh-frequency treatment on a biological tissue, the operation methodcomprising: causing, by a control circuit, a high-frequency electricpower source circuit to output electric power; acquiring, by the controlcircuit, an initial impedance value which is a value relating to animpedance of the biological tissue, in a first period from a start ofthe output; determining, by the control circuit, an increase rate of anoutput voltage relative to time, based on the initial impedance value;increasing, by the control circuit, the output voltage of thehigh-frequency electric power source circuit in accordance with theincrease rate in a second period following the first period; acquiring,by the control circuit, the value relating to the impedance of thebiological tissue in the second period; and terminating, by the controlcircuit, the second period after the value relating to the impedancereaches a minimum value, wherein in the second period, the outputvoltage is increased linearly with time, and, as the initial impedancevalue becomes greater, the increase rate is made smaller.
 2. (canceled)3. (canceled)
 4. The operation method of claim 1, wherein the increaserate is determined to be such a value that a length of the second periodfalls within a predetermined range, regardless of the initial impedancevalue.
 5. The operation method of claim 4, wherein the predeterminedrange of the length of the second period is 0.5 seconds to 1.5 seconds.6. An electric power source device for operating a high-frequencytreatment instrument configured to perform a high-frequency treatment ona biological tissue, the device comprising: a high-frequency electricpower source circuit configured to output electric power; an outputdetection circuit configured to detect the output; and a control circuitconfigured to acquire a value relating to the output from the outputdetection circuit, and configured to control an operation of thehigh-frequency electric power source circuit, the control circuit beingconfigured to execute: causing the high-frequency electric power sourcecircuit to output the electric power; acquiring, based on the valuerelating to the output acquired from the output detection circuit, aninitial impedance value which is a value relating to an impedance of thebiological tissue, in a first period from a start of the output;determining an increase rate of an output voltage relative to time,based on the initial impedance value; increasing the output voltage ofthe high-frequency electric power source circuit in accordance with theincrease rate in a second period following the first period; acquiringthe value relating to the impedance of the biological tissue in thesecond period; and terminating the second period after the valuerelating to the impedance reaches a minimum value, wherein in the secondperiod, the output voltage is increased linearly with time, and, as theinitial impedance value becomes greater, the increase rate is madesmaller.
 7. A high-frequency treatment system comprising: the electricpower source device of claim 6; and the high-frequency treatmentinstrument.